Sod harvesting for commercial applications typically occurs by cutting strips of sod from the ground using a tractor-driven sod harvester. The cut strips are formed into rolls and stacked for pick up and transportation in bulk.
Mechanisms to automatically roll strips of sod have existed for many years. The sod rolls are generally discharged at the rear, upper end of an inclined transport conveyor. The rolls are preferably discharged in a location convenient for a worker to pick up the rolls of sod and stack them onto a pile, usually on a pallet carried by the sod harvester.
For example, U.S. Pat. No. 3,509,944 (Brouwer et al.) discloses a prior art sod harvester which includes such an inclined conveyor, and in which the rolls of sod are formed adjacent the upper end of the conveyor.
U.S. Pat. No. 4,832,130 (Brouwer et al.) discloses a self-propelled sod harvester. The harvester includes an inclined conveyor, and the conveyor delivers the strips of sod into a separate roll-forming enclosure. The roll-forming enclosure includes a pair of conveyors disposed generally at right angles to one another for forming the roll. The formed rolls are discharged onto a cart at the end of the harvester which can convey the formed roll to either side of the cart and clear of the harvester for its next pass.
The position of the flap, or outside end of the roll, becomes important for the worker, commonly called a “stacker”, who lifts and transports the rolls of sod. FIG. 1 depicts a side view of a sod roll 1 after discharge from the roll-up mechanism onto a platform 2 or conveyor (not shown). If the flap 3 is located too far clockwise, it could fall down, partially unrolling the roll of sod. If it is located too far counterclockwise, a flap may hang down as it is picked up for stacking, which may be inconvenient to the stacker. Stackers typically prefer to have the flap located consistently to make their handling of the roll more predictable. The flap location becomes more important when the roll of sod will be handled mechanically, as with the robotic sod stacker, such as in a related application entitled “Robotic Sod Stacker” and filed on the filing date of the present application.
One common method of rolling a strip of sod utilizes a roll-up conveyor 5, which is located at the rear upper end of the transport conveyor 4. Ahead of the roll-up conveyor, the sod roll is started by catching and turning back the leading edge on a curved piece of expanded metal 6, typically referred to as a starter gate. The sod continues to roll under a tray 7 that provides sufficient friction to hold the top of the newly started roll generally stationary as the transport conveyor 4 moves the sod rearward (to the left in FIG. 1). As the roll moves rearward and grows, it encounters the roll-up conveyor 5, which is located above the transport conveyor 4. Roll-up conveyor 5 operates on a parallel plane but moves in a direction opposite and at a slightly slower speed than transport conveyor 4. This allows the sod roll 1 to finish being rolled in a smaller bundle than would be required if only a tray were used.
As the sod roll 1 is completed at the end of roll-up conveyor 5, it can be ejected from between the two conveyors 4, 5 by a plate 8 positioned close to the end of the roll-up conveyor. When sod roll 1 encounters plate 8, it is displaced away from the roll-up conveyor 5, and the transport conveyor 4 ejects the sod roll 1 rearward. The position of the flap can be controlled by the adjustable position of plate 8. As plate 8 moves further forward (to the right in FIG. 1), sod roll 1 will be ejected sooner, and as plate 8 moves rearward (to the left), sod roll 1 will be ejected later.
This apparatus and method of flap control has generally proven to be effective for most manual stacking conditions. However, even with the flap control plate 8 held stationary, the flap position may still change due to variations in sod thickness, length of the strip, and amount of slip between the sod and the two conveyors. Some designs have attempted to make the flap position easier to control than designs that require relocating the plate. For example, Nannings Van Loon has developed a mechanism which can move the flap adjuster plate back and forth using an electric actuator and a toggle switch. Brouwer turf Equipment also offers a variable speed hydraulically-driven roll-up conveyor, which can easily be adjusted to control the flap position. Both of these methods, however, require manual intervention to correct the flap position. Automated stacking requires automatic flap control.
All previous methods have been based on an assumed consistent location of the leading edge of the sod strip, consistent length, and consistent thickness. This greatly controls the location of the flap by varying the amount of time the sod roll sends in the roll-up conveyor or by the speed of the roll-up conveyor.